1. Field of the Invention
The present invention relates to a chair assembly, and more particularly to a chair assembly that has a backrest-adjusting device providing the backrest with resilient force against a user's back. The backrest-adjusting device is capable of adjusting the resilient force for different users.
2. Description of Related Art
Chairs are an important piece of furniture commonly used in people's daily lives to provide people with comfort and facilitation when they sit thereon.
A conventional chair has a supporting base, a seat, a backrest and two handrails. The seat is mounted on the supporting base. The backrest is mounted on the supporting base behind the seat. The handrails are mounted oppositely on the seat. But the conventional chair cannot adjust the angle of the backrest relative to the seat for different users.
Another kind of conventional chair has been developed to allow users to change the angle of the backrest. Furthermore, a spring is mounted between the backrest and the seat to provide backrest with resilient force against a user's back. When using the chair, the user's back abuts the backrest against the resilient force and changes the angle of the backrest so that after a balance between the resilient force and the user's pressing force is achieved, the user adjusts to an optimal sitting position and the backrest stops at a specific angle.
However, the resilient force corresponding to each angle of the backrest is constant and cannot be adjusted. Different users need to apply the same pressing force against the resilient force to hold the backrest at a same angle. A relative able-bodied and heavy user may feel that the resilient force from the backrest is insufficient and the backrest is too soft to hold his/her body. On the other hand, a relative small and light user may feel that the resilient force from the backrest is excessive and the backrest is to too hard. In other words, the chair cannot adapt to different users.
To overcome the shortcomings, the present invention provides a chair assembly with a backrest-adjusting device to mitigate or obviate the aforementioned problems.